Method of Manufacturing Fluid-Filled Chambers

ABSTRACT

A method includes positioning a first polymer sheet on a substantially first flat surface of a tool, positioning a second polymer sheet on the first polymer sheet, and moving a second substantially flat surface of the tool into contact with the second polymer sheet. The method also includes maintaining a gap between the first polymer sheet and the second polymer sheet at a predetermined area and heating one of the two substantially flat surfaces of the tool to heat one of the first polymer sheet and the second polymer sheet. The method further includes joining the first polymer sheet and the second polymer sheet together at locations outside of the predetermined area to define a peripheral bond of the chamber.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.17/527,922, filed Nov. 16, 2021, which is a continuation of U.S. patentapplication Ser. No. 16/289,161, filed Feb. 28, 2019, which claimspriority to U.S. Provisional Application No. 62/636,883, filed Mar. 1,2018, the contents of which are hereby incorporated by reference intheir entirety.

FIELD

The present disclosure relates to methods of manufacturing fluid-filledchambers and more particularly to methods of manufacturing fluid-filledchambers for incorporation into articles of footwear.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

Articles of footwear conventionally include an upper and a solestructure. The upper may be formed from any suitable material(s) toreceive, secure, and support a foot on the sole structure. The upper maycooperate with laces, straps, or other fasteners to adjust the fit ofthe upper around the foot. A bottom portion of the upper, proximate to abottom surface of the foot, attaches to the sole structure.

Sole structures generally include a layered arrangement extendingbetween a ground surface and the upper. One layer of the sole structureincludes an outsole that provides abrasion-resistance and traction withthe ground surface. The outsole may be formed from rubber or othermaterials that impart durability and wear-resistance, as well asenhancing traction with the ground surface. Another layer of the solestructure includes a midsole disposed between the outsole and the upper.The midsole provides cushioning for the foot and may include apressurized fluid-filled chamber that compresses resiliently under anapplied load to cushion the foot by attenuating ground-reaction forces.

Fluid-filled chambers are generally formed from two polymer sheets ofmaterial that join together to define a peripheral bond of thefluid-filled chambers. A pressurized fluid is then supplied between thetwo polymer sheets to inflate the chamber. A tool having upper and lowermold portions is generally used to impart a desired shape of the chamberand apply heat for joining the two polymer sheets together. Generally,for a fluid-filled chamber tailored for a specific article of footwear,multiple tools need to be designed and produced to manufacturefluid-filled chambers for each shoe size. Moreover, mold tools aregenerally specific to the desired shape and, therefore, separate moldtools need to be designed and produced for manufacturing fluid-filledchambers with different shapes.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected configurations and are not intended to limit the scope of thepresent disclosure.

FIG. 1 is a top perspective view of an article of footwear in accordancewith principles of the present disclosure;

FIG. 2 is an exploded view of the article of footwear of FIG. 1 showinga fluid-filled chamber incorporating a tensile element received within acavity between an inner surface of an outsole and a bottom surface of astrobel;

FIG. 3 is a perspective view of a heat press tool including a lowerplaten and an upper platen movable relative to the lower platen betweenan open position and a closed position in accordance with principles ofthe present disclosure;

FIG. 4 is a schematic view of the heat press tool of FIG. 3 showing afirst polymer sheet positioned on a substantially first flat surface ofthe lower platen and a second polymer sheet positioned on the firstpolymer sheet when the heat press tool is in the open position;

FIG. 5 is a schematic view of the heat press tool of FIG. 3 showing thefirst polymer sheet and the second polymer sheet positioned between thefirst flat surface and the second flat surface and the second polymersheet heated by the second flat surface when the heat press tool is inthe closed position;

FIG. 6 is a schematic view of the heat press tool of FIG. 3 showing theheat press tool in the open position and the first polymer sheet and thesecond polymer sheet joined together to define a peripheral bond;

FIG. 7 is a schematic view of the heat press tool of FIG. 3 showing thesecond polymer sheet positioned on the substantially first flat surfaceof the lower platen and bonded to a tensile layer of a tensile elementwith the heat press tool is in the open position;

FIG. 8 is a schematic view of the heat press tool of FIG. 3 showing thefirst polymer sheet and the second polymer sheet positioned between thefirst flat surface and the second flat surface and the first polymersheet heated by the second flat surface when the heat press tool is inthe closed position;

FIG. 9 is a schematic view of the heat press tool of FIG. 3 showing theheat press tool in the open position and the first polymer sheet and thesecond polymer sheet bonded to respective tensile layers of the tensileelement;

FIG. 10 is a top perspective view of an article of footwear inaccordance with principles of the present disclosure;

FIG. 11 is an exploded view of the article of footwear of FIG. 10showing a fluid-filled chamber received within a cavity between an innersurface of an outsole and a bottom surface of a strobel;

FIG. 12 is a perspective view of a jig defining an interior void inaccordance with principles of the present disclosure;

FIG. 13 is a top view of the jig of FIG. 12 ;

FIG. 14 is a schematic view of a heat press tool showing the jig of FIG.12 positioned on a substantially first flat surface of the tool, a firstpolymer sheet positioned on the jig, and a second polymer sheetpositioned on the first polymer sheet when the heat press tool is in anopen position;

FIG. 15 is a schematic view of the heat press tool of FIG. 14 showingthe first polymer sheet and the second polymer sheet maintaining a gapat locations within the interior void of the jig when the heat presstool is in a closed position;

FIG. 16 is a schematic view of the heat press tool of FIG. 14 showingthe heat press tool in the open position and the first polymer sheet andthe second polymer sheet joined together to define a peripheral bond;

FIG. 17 is a schematic view of the heat press tool of FIG. 14 showingthe jig rotated 180° and the second polymer sheet positioned on the jigwhen the heat press tool is in the open position;

FIG. 18 is a schematic view of the heat press tool of FIG. 14 showingthe first polymer sheet and the second polymer sheet maintaining the gapat locations within the interior void of the jig when the heat presstool is in the closed position;

FIG. 19 is a schematic view of the heat press tool of FIG. 14 showingthe heat press tool in the open position and the first polymer sheet andthe second polymer sheet joined together to define the peripheral bond;

FIG. 20 is a perspective view of a jig defining an interior void inaccordance with principles of the present disclosure;

FIG. 21 is a top view of the jig of FIG. 20 ;

FIG. 22 is a schematic view of a heat press tool showing the jig of FIG.20 positioned on a substantially first flat surface of the tool, a firstpolymer sheet positioned on the jig, and a second polymer sheetpositioned on the first polymer sheet when the heat press tool is in anopen position;

FIG. 23 is a schematic view of the heat press tool of FIG. 22 showingthe first polymer sheet and the second polymer sheet maintaining a gapat locations within the interior void of the jig when the heat presstool is in a closed position;

FIG. 24 is a schematic view of the heat press tool of FIG. 22 showingthe heat press tool in the open position and the first polymer sheet andthe second polymer sheet joined together to define a peripheral bond;

FIG. 25 is a schematic view of the heat press tool of FIG. 22 showingthe second polymer sheet positioned on the jig when the heat press toolis in the open position;

FIG. 26 is a schematic view of the heat press tool of FIG. 22 showingthe first polymer sheet and the second polymer sheet maintaining the gapat locations within the interior void of the jig when the heat presstool is in the closed position;

FIG. 27 is a perspective view of the heat press tool of FIG. 22 showingthe heat press tool in the open position after forming the fluid-filledchamber by joining the first polymer sheet to the second polymer sheetto define the peripheral bond;

FIG. 28 is a schematic view of a heat press tool showing a jigpositioned on a substantially first flat surface of the jig, a firstthermoformed polymer sheet positioned on the jig, and a secondthermoformed polymer sheet positioned on the first thermoformed polymersheet when the heat press tool is in an open position;

FIG. 29 is a schematic view of the heat press tool of FIG. 28 showingthe first thermoformed polymer sheet and the second thermoformed polymersheet nested within an interior void of the jig when the heat press toolis in a closed position;

FIG. 30 is a schematic view of the heat press tool of FIG. 28 showingthe heat press tool in the open position and the first thermoformedpolymer sheet and the second thermoformed polymer sheet joined togetherto define a peripheral bond;

FIG. 31 is schematic view of a chamber formed by joining the firstthermoformed polymer sheet to the second thermoformed polymer sheet todefine the peripheral bond and a fluid source configured to supplypressurized fluid into the chamber;

FIG. 32 is a schematic view of the fluid source of FIG. 31 inflating thechamber with pressurized fluid; and

FIG. 33 is a perspective view of the fluid-filled chamber of FIG. 32showing the first polymer sheet and the second polymer sheet joinedtogether to define the peripheral bond.

Corresponding reference numerals indicate corresponding parts throughoutthe drawings.

DETAILED DESCRIPTION

Example configurations will now be described more fully with referenceto the accompanying drawings. Example configurations are provided sothat this disclosure will be thorough, and will fully convey the scopeof the disclosure to those of ordinary skill in the art. Specificdetails are set forth such as examples of specific components, devices,and methods, to provide a thorough understanding of configurations ofthe present disclosure. It will be apparent to those of ordinary skillin the art that specific details need not be employed, that exampleconfigurations may be embodied in many different forms, and that thespecific details and the example configurations should not be construedto limit the scope of the disclosure.

The terminology used herein is for the purpose of describing particularexemplary configurations only and is not intended to be limiting. Asused herein, the singular articles “a,” “an,” and “the” may be intendedto include the plural forms as well, unless the context clearlyindicates otherwise. The terms “comprises,” “comprising,” “including,”and “having,” are inclusive and therefore specify the presence offeatures, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features, steps,operations, elements, components, and/or groups thereof. The methodsteps, processes, and operations described herein are not to beconstrued as necessarily requiring their performance in the particularorder discussed or illustrated, unless specifically identified as anorder of performance. Additional or alternative steps may be employed.

When an element or layer is referred to as being “on,” “engaged to,”“connected to,” “attached to,” or “coupled to” another element or layer,it may be directly on, engaged, connected, attached, or coupled to theother element or layer, or intervening elements or layers may bepresent. In contrast, when an element is referred to as being “directlyon,” “directly engaged to,” “directly connected to,” “directly attachedto,” or “directly coupled to” another element or layer, there may be nointervening elements or layers present. Other words used to describe therelationship between elements should be interpreted in a like fashion(e.g., “between” versus “directly between,” “adjacent” versus “directlyadjacent,” etc.). As used herein, the term “and/or” includes any and allcombinations of one or more of the associated listed items.

The terms first, second, third, etc. may be used herein to describevarious elements, components, regions, layers and/or sections. Theseelements, components, regions, layers and/or sections should not belimited by these terms. These terms may be only used to distinguish oneelement, component, region, layer or section from another region, layeror section. Terms such as “first,” “second,” and other numerical termsdo not imply a sequence or order unless clearly indicated by thecontext. Thus, a first element, component, region, layer or sectiondiscussed below could be termed a second element, component, region,layer or section without departing from the teachings of the exampleconfigurations.

One aspect of the disclosure provides a method of forming a chamber. Themethod includes positioning a first polymer sheet on a substantiallyfirst flat surface of a tool, positioning a second polymer sheet on thefirst polymer sheet, and moving a second substantially flat surface ofthe tool into contact with the second polymer sheet. The method alsoincludes maintaining a gap between the first polymer sheet and thesecond polymer sheet at a predetermined area and heating one of the twosubstantially flat surfaces of the tool to heat one of the first polymersheet and the second polymer sheet. The method further includes joiningthe first polymer sheet and the second polymer sheet together atlocations outside of the predetermined area to define a peripheral bondof the chamber.

Implementations of the disclosure may include one or more of thefollowing optional features. In some implementations, maintaining thegap between the first polymer sheet and the second polymer sheetincludes adding a tensile element defining the predetermined areabetween the first polymer sheet and the second polymer sheet. The methodmay also include heating the one of the two substantially flat surfacesof the tool to heat an entire surface of the one of the two polymersheets.

Adding the tensile element defining the predetermined area between thefirst polymer sheet and the second polymer sheet may include positioninga first tensile layer of the tensile element in contact with the firstpolymer sheet and positioning a second tensile layer of the tensileelement in contact with the second polymer sheet. Heating one of the twosubstantially flat surfaces of the tool may bond one of the firstpolymer sheet and the second polymer sheet to a respective one of thefirst tensile layer and the second tensile layer.

In some examples, the method includes moving the second substantiallyflat surface of the tool away from the second polymer sheet afterjoining the first polymer sheet and the second polymer sheet andpositioning the second polymer sheet on the substantially first flatsurface of the tool. The method may also include moving the secondsubstantially flat surface of the tool into contact with the firstpolymer sheet and heating the one of the two substantially flat surfacesof the tool to heat the other of the first polymer sheet and the secondpolymer sheet.

Heating the other of the first polymer sheet and the second polymersheet may cause the other of the first polymer sheet and the secondpolymer sheet to bond to a respective one of the first tensile layer andthe second tensile layer. In some examples, the method includes heatingthe other of the two substantially flat surfaces of the tool to heat asurface of the other of the first polymer sheet and the second polymersheet. Joining the first polymer sheet and the second polymer sheettogether at locations outside of the predetermined area may includejoining the first polymer sheet to the first tensile layer and joiningthe second polymer sheet to the second tensile layer at locations withinthe predetermined area.

In some examples, the method includes positioning a jig between thefirst polymer sheet and the substantially first flat surface of thetool. Maintaining the gap between the first polymer sheet and the secondpolymer sheet at the predetermined area may include maintaining the gapbetween the first polymer sheet and the second polymer sheet within avoid defined by the jig. The method may further include supplying apressurized fluid into an area between the first polymer sheet and thesecond polymer sheet after joining the first polymer sheet and thesecond polymer sheet together to inflate the chamber.

Another aspect of the disclosure provides another method of forming achamber. The method includes positioning a jig defining an interior voidin a first position on a first surface of a tool, positioning a firstpolymer sheet on the jig, and positioning a second polymer sheet on thefirst polymer sheet. The method also includes moving a second surface ofthe tool into contact with the second polymer sheet, heating the tool toheat one of the first polymer sheet and the second polymer sheet, andjoining the first polymer sheet and the second polymer sheet together atlocations outside of the interior void defined by the jig to define aperipheral bond of the chamber.

This aspect may include one or more of the following optional features.In some implementations, the method includes maintaining a gap betweenthe first polymer sheet and the second polymer sheet. The gap may have apredetermined area including a shape defined by the interior void of thejig. Heating the tool to heat one of the first polymer sheet and thesecond polymer sheet may include heating the second surface of the toolto heat the second polymer sheet.

In some examples, the method includes moving the second surface of thetool away from the second polymer sheet after heating the second polymersheet, positioning the second polymer sheet on the jig, moving thesecond surface of the tool into contact with the first polymer sheet,and heating the second surface of the tool to heat the first polymersheet. Positioning the second polymer sheet on the jig may includepositioning the peripheral bond on the jig.

The method may also include moving the second surface of the tool awayfrom the second polymer sheet after heating the second polymer sheet,rotating the jig 180°, and positioning the jig in a second position onthe first surface of the tool after rotating the jig 180°. The methodmay further include positioning the second polymer sheet on the jig,moving the second surface of the tool into contact with the firstpolymer sheet, heating the second surface of the tool to heat the firstpolymer sheet, and joining the first polymer sheet and the secondpolymer sheet together at locations outside of the interior void definedby the jig to define the peripheral bond of the chamber.

In some implementations, the method includes maintaining the gap betweenthe first polymer sheet and the second polymer sheet at thepredetermined area within the interior void defined by the jig.Positioning the second polymer sheet on the jig may include positioningthe peripheral bond on the jig when the jig is in the second position.The method may also include supplying a pressurized fluid into an areabetween the first polymer sheet and the second polymer sheet afterjoining the first polymer sheet and the second polymer sheet together toinflate the chamber.

In some configurations, positioning the first polymer sheet on the jigincludes positioning a first thermoformed polymer sheet on the jig. Inthese configurations, positioning the second polymer sheet on the firstpolymer sheet may include positioning a second thermoformed polymersheet on the first thermoformed polymer sheet. In some examples,positioning the second polymer sheet on the first polymer sheet includespositioning the second polymer sheet that is not thermoformed on thefirst thermoformed polymer sheet. In these examples, gravity may causethe second polymer sheet to sag relative to the first thermoformedpolymer sheet.

Referring to FIGS. 1 and 2 , an article of footwear 10 is provided andincludes an upper 100 and a sole structure 200 attached to the upper100. The article of footwear 10 may be divided into one or moreportions. The portions may include a forefoot portion 12, a mid-footportion 14, and a heel portion 16. The forefoot portion 12 maycorrespond with toes and joints connecting metatarsal bones with phalanxbones of a foot. The mid-foot portion 14 may correspond with an archarea of the foot, and the heel portion 16 may correspond with rearportions of the foot, including a calcaneus bone. The footwear 10 mayinclude lateral and medial sides 18, 20, respectively, correspondingwith opposite sides of the footwear 10 and extending through theportions 12, 14, 16.

The upper 100 includes interior surfaces that define an interior void102 that receives and secures a foot for support on the sole structure200. An ankle opening 104 in the heel portion 16 may provide access tothe interior void 102. For example, the ankle opening 104 may receive afoot to secure the foot within the void 102 and facilitate entry andremoval of the foot to and from the interior void 102. In some examples,one or more fasteners 106 extend along the upper 100 to adjust a fit ofthe interior void 102 around the foot while concurrently accommodatingentry and removal of the foot therefrom. The upper 100 may includeapertures such as eyelets and/or other engagement features such asfabric or mesh loops that receive the fasteners 106. The fasteners 106may include laces, straps, cords, hook-and-loop, or any other suitabletype of fastener.

The upper 100 may include a tongue portion 110 that extends between theinterior void 102 and the fasteners 106. The upper 100 may be formedfrom one or more materials that are stitched or adhesively bondedtogether to form the interior void 102. Suitable materials of the uppermay include, but are not limited, textiles, foam, leather, and syntheticleather. The materials may be selected and located to impart propertiesof durability, air-permeability, wear-resistance, flexibility, andcomfort.

In some implementations, the sole structure 200 includes an outsole 210and a strobel 220 arranged in a layered configuration. The solestructure 200 (e.g., the outsole 210 and the strobel 220) defines alongitudinal axis L. For example, the outsole 210 engages with a groundsurface during use of the article of footwear 10 and the strobel 220 isdisposed between the upper 100 and the outsole 210. In some examples,the sole structure 200 may also incorporate additional layers such as aninsole or sockliner (neither shown), which may reside within theinterior void 102 of the upper 100 to receive a plantar surface of thefoot to enhance the comfort of the footwear 10. In some examples, asidewall 230 surrounds a perimeter of the outsole 210 and separates theoutsole 210 and the strobel 220 to define a cavity 240 therebetween.

In some configurations, the cavity 240 receives a fluid-filled chamber300 filled with a pressurized fluid such as air, nitrogen, helium,sulfur, hexafluoride, or liquids/gels to enhance cushioningcharacteristics of the footwear 10 in response to ground-reactionforces. The fluid-filled chamber 300 defines an interior cavity thatreceives the pressurized fluid while providing a durable sealed barrierfor retaining the pressurized fluid therein. The chamber 300 may includea lower barrier portion 301 that opposes the outsole 210 and an upperbarrier portion 302 disposed on an opposite side of the chamber 300 thanthe lower barrier portion 301 and opposing the strobel 220. The lowerbarrier portion 301 may correspond to a first polymer sheet and theupper barrier portion 302 may correspond to a second polymer sheet thatjoins to the first polymer sheet to define a peripheral bond 350 (FIGS.6-9 ) of the chamber 300. Here, the peripheral bond 350 defines apredetermined area associated with the interior cavity that receives andretains the pressurized fluid therein. Accordingly, the peripheral bond350 forms a sidewall 303 that extends around the periphery of thechamber 300 to connect the lower barrier portion 301 to the upperbarrier portion 302.

In some configurations, the interior cavity of the fluid-filled chamber300 also receives a tensile element 400 having a lower tensile layer 401that attaches to lower barrier portion 301, an upper tensile layer 402that attaches to the upper barrier portion 302, and a plurality oftensile elements 430 that extend between the lower and upper tensilelayers 401 and 402, respectively, of the tensile element 400.Thermobonding may be used to secure the tensile element 400 to thechamber 300. The tensile element 400 is operative to prevent the chamber300 from expanding outward or otherwise distending due to the pressureof the fluid within the internal cavity of the chamber 300. Namely, thetensile element 400 may limit expansion of the chamber 300 when underpressure to retain an intended shape of surfaces of the barrier portions301 and 302.

The chamber 300 may define a length that extends substantially parallelto the longitudinal axis L of the sole structure 200 and may be formedto provide contours that conform to a profile of the bottom surface ofthe foot as well as an inner surface 214 of the outsole 210. In someconfigurations, the chamber 300 defines a length that only extendsthrough a portion of the length of the sole structure 200. For instance,the chamber 300 may reside in the heel portion 16 of the sole structure200 to provide cushioning for the heel of the foot. Additionally oralternatively, two or more chambers 300 may reside in the sole structure200 each defining a length that extends along a portion of the length ofthe sole structure 200. In other configurations, two or more chambers300 may be layered upon one another that react differently in responseto ground-reaction forces to provide gradient cushioning for the foot.While the sole structure 200 may include more than one chamber 300, thesole structure 200 will be described and shown as including a singlechamber 300 that extends along the longitudinal axis L from the forefootportion 12 to the heel portion 16.

The outsole 210 may include a ground-engaging surface 212 and theopposite inner surface 214. The outsole 210 may attach to the upper 100.In some examples, the sidewall 230 extends from the perimeter of theoutsole 210 and attaches to the strobel 220 or the upper 100. Theexample of FIG. 1 shows the outsole 210 attaching to the upper 100proximate to a tip of the forefoot portion 12. The outsole 210 generallyprovides abrasion-resistance and traction with the ground surface duringuse of the article of footwear 10. The outsole 210 may be formed fromone or more materials that impart durability and wear-resistance, aswell as enhance traction with the ground surface. For example, rubbermay form at least a portion of the outsole 210.

The strobel 220 may include a bottom surface 222 and a footbed 224disposed on an opposite side of the strobel 220 than the bottom surface222. Stitching 226 or adhesives may secure the strobel 220 to the upper100. The footbed 224 may be contoured to conform to a profile of thebottom surface (e.g., plantar) of the foot. The bottom surface 222 mayoppose the inner surface 214 of the outsole 210 to define the cavity 240therebetween. The strobel 220 may be formed from a flexible materialthat allows the strobel 220 to conform to the fluid-filled chamber 300residing in the cavity 240 underneath the strobel 220. In so doing, theflexible strobel 220 allows the pressurized fluid retained by thefluid-filled chamber 300 within in the cavity 240 to interact with theprofile of the bottom surface of a foot during gradient loading of thesole structure 200. In some examples, the sidewall 230 may define aperimeter of the cavity 240 as well as a depth of the cavity 240 basedon a length of separation between the bottom surface 222 and the innersurface 214. One or more polymer foam materials may form the sidewall230 to provide resilient compressibility under applied loads toattenuate ground-reaction forces.

FIG. 2 provides an exploded view of the article of footwear 10 showingthe fluid-filled chamber 300 retaining the pressurized fluid (e.g.,air), the inner surface 214 of the outsole 210, and the bottom surface222 of the strobel 220. The length of the chamber 300 may extend betweena first end 311 and a second end 312. The first end 311 may be disposedproximate to the heel portion 16 of the sole structure 200 and thesecond end 312 may be disposed proximate to the forefoot portion 12 ofthe sole structure 200. The chamber 300 may also include a thicknessextending substantially perpendicular to the longitudinal axis L of thesole structure 200 and a width extending between the lateral side 18 andthe medial side 20. Accordingly, the length, the width, and thethickness of the chamber 300 may substantially occupy the cavity 240defined by the inner surface 214 and the bottom surface 222 and mayextend through the forefoot, mid-foot, and heel portions 12, 14, 16,respectively, of the outsole 210.

FIG. 3 is a perspective view of a heat press tool 500 for use inmanufacturing the fluid-filled chamber 300 by applying heat and pressureto join the lower barrier portion 301 (e.g., first polymer sheet) andthe upper barrier portion 302 (e.g., second polymer sheet) together todefine the peripheral bond 350 of the chamber 300. In configurationswhen the chamber 300 includes the tensile element 400 for limitingexpansion of the chamber 300 when the pressurized fluid (e.g., air) issupplied into the internal cavity, the application of heat and pressureby the heat press tool 500 is also operative to bond the lower barrierportion 301 and the upper barrier portion 302 to respective ones of thelower tensile layer 401 and the upper tensile layer 402.

The heat press tool 500 includes a housing 510 having a top section 512and a base section 514. A lower platen 516 rigidly attaches to the basesection 514 and includes a substantially first flat (planar) surface501, while an upper platen 518 pivotally attaches to the top section 512of the housing 512 via an elongate actuation handle 520 and includes asubstantially second flat (planar) surface 502. The actuation handle 520has a proximal end pivotally attached to the top section 512 of thehousing 510 and a distal end having a gripper portion 522. Accordingly,the upper platen 518 is reciprocally movable by the actuation handle 520relative to the lower platen 516 to operate the tool 500 between an openposition when the upper platen 518 is furthest away from the lowerplaten 516 and a closed position when the upper platen 518 is verticallyaligned and proximate to the lower platen 516 such that the first flatsurface 501 and the second flat surface 502 are opposing, and in someinstances, contacting one another. In some configurations, the actuationhandle 520 is omitted and one or both of the upper and lower platens 516and 518 move relative to one another between the open and closedpositions in a fully automated manner through the use of one or moreactuating mechanisms (none shown).

FIG. 3 shows the upper platen 518 including one or more heating elements530 disposed therein that are operable to selectively raise atemperature of the second flat surface 502. As shown in FIG. 3 , suchheating elements are not included in the lower platen 516. In otherconfigurations, however, the lower platen 516 may include one or moreheating elements 530 for selecting raising a temperature of the firstflat surface 501 while the upper platen 518 may also include the heatingelements 530 or omit the heating elements 530. While in the closedposition, the first and second flat surfaces 501 and 502 of the tool 500are operative to apply sufficient heat and pressure for joining thefirst and second polymer sheets 301 and 302 together and, thus, definethe peripheral bond 350 of the fluid-filled chamber 300. In someconfigurations, the tensile element 400 defines a predetermined area 340(FIG. 4 ) and is operative to maintain a gap G between the polymersheets 301 and 302 at the predetermined area 340 such that the sheets301 and 302 only join together at locations outside of the predeterminedarea 340. In other configurations, a jig 700 (FIG. 12 ) is positionedbetween the first flat surface 501 and the first polymer sheet 301 andthe gap G between the sheets 301 and 302 is maintained within aninterior void 720 (FIG. 12 ) defined by the jig 700. In someimplementations, the tool 500 includes a power cord 550 configured toprovide power to the tool 500 from an external power source (not shown)for energizing the heating elements 530 to heat the second flat surface501 to a desired temperature. In other implementations, the tool 500includes an energy storage device (e.g., a battery; not shown) forproviding power to energize the heating elements 530. The tool 500 mayalso include data processing hardware 552 for setting the desiredtemperature of the second flat surface 501.

Referring to FIGS. 4-9 , schematic views of the heat press tool 500 ofFIG. 3 are provided and include the lower platen 516 and the upperplaten 518 operable between the open and closed positions for joiningthe first polymer sheet 301 and the second polymer sheet 302 together todefine the peripheral bond 350 of the fluid-filled chamber 300. As setforth above, the fluid-filled chamber 300 may be incorporated into thearticle of footwear 10 of FIGS. 1 and 2 once formed and inflated.

The lower platen 516 includes the substantially first flat surface 501and the upper platen 518 includes the substantially second flat surface502 and the one or more heating elements 530 disposed therein forraising the temperature (e.g., heating) the second flat surface 502. Thelower platen 516 may additionally or alternatively include heatingelements for raising the temperature of the first flat surface 501without departing from the scope of the present disclosure. In someexamples, the lower platen 516 is fixed and the upper platen 518translates toward the lower platen 516 to close the heat press tool 500and thereby apply pressure and heat to the first and second polymersheets 301 and 302 disposed therebetween. In other examples, the lowerplaten 516 and the upper platen 518 may each translate toward oneanother or only the lower patent 516 may translate toward the upperplaten 518.

FIG. 4 shows the tool 500 open and the first polymer sheet 301positioned on the substantially first flat surface 501 of the tool 500,the second polymer sheet 302 positioned on the first polymer sheet 301,and the tensile element 400 defining the predetermined area 340 disposedbetween the first polymer sheet 301 and the second polymer sheet 302.More specifically, the first tensile layer 401 of the tensile element400 is positioned in contact with the first polymer sheet 301 and thesecond tensile layer 402 of the tensile element 400 is positioned incontact with the second polymer sheet 302. The tensile members 430 maybe disposed between and connecting the tensile layers 401 and 402. Aswill become apparent, the tensile element 400 is operative to maintainthe gap G between the first polymer sheet 301 and the second polymersheet 302 at the predetermined area 340 such that the first polymersheet 301 and the second polymer sheet 302 are prevented from joining,or otherwise bonding, to one another at locations within thepredetermined area 340. In operation, the upper platen 518 and secondflat surface 502 thereof may be moved to the open position in order toexpose the first flat surface 501 of the lower platen 516. In someexamples, the heating elements 530 begin to heat the second flat surface502 to a predetermined temperature while the tool 500 is open. As such,the second flat surface 502 may be at a predetermined temperature priorto engaging the second polymer sheet 302.

The tool 500 may be closed by selectively moving the actuation handle520 to translate the upper platen 518 toward the lower platen 516. FIG.5 shows the tool 500 closed by moving the second substantially flatsurface 502 of the upper platen 518 into contact with the second polymersheet 302. Moving the second flat surface 502 into contact with thesecond polymer sheet 302 causes the first polymer sheet 301, the secondpolymer sheet 302, and the tensile element 400 to compress between thefirst flat surface 501 and the second flat surface 502 of the heatingtool 500. The tensile element 400 is operative to maintain the gap Gbetween the first polymer sheet 301 and the second polymer sheet 302 atthe predetermined area 340 while the first polymer sheet 301 and thesecond polymer sheet 302 contact one another at locations outside of thepredetermined area 340. Concurrently, the heating elements 530associated with the upper platen 518 apply heat 532 to heat the secondflat surface 502 of the tool 500 to a predetermined temperature, therebyheating the second polymer sheet 302 in contact therewith. In someexamples, heating the second flat surface 502 of the tool 500 includesheating an entire surface of the second flat surface 502. Thepredetermined temperature includes a temperature suitable for allowingthe second polymer sheet 302 to bond with the second tensile layer 402of the tensile element 400 at the locations within the predeterminedarea 340, while simultaneously joining with the first polymer sheet 301at the locations outside of the predetermined area 340 to define theperipheral bond 350 of the chamber 300. In other examples, the lowerplaten 516 includes heating elements for heating the first flat surface501 to heat the first polymer sheet 301 in contact therewith to bondwith the first tensile layer 401 of the tensile element 400.

FIG. 6 shows the heating press tool 500 in the open position by movingthe second substantially flat surface 502 of the upper platen 518 awayfrom the second polymer sheet 302 after joining the first polymer sheet301 and the second polymer sheet 302 to define the peripheral bond 350.The heat applied by the second substantially flat surface 502 while incontact with the second polymer sheet 302 also allows the second polymersheet 302 to bond to the second tensile layer 402 of the tensile element400. In some examples, the heat applied by the second substantially flatsurface while in contact with the second polymer sheet 302 is alsosufficient to allow the first polymer sheet 301 to bond to the firsttensile layer 401 of the tensile element 400. In other examples,however, no thermal bonding between the first polymer sheet 301 and thefirst tensile layer 401 of the tensile element 400 has occurred.Accordingly, the first polymer sheet 301 must also be heated by thesecond substantially flat surface 502 of the tool 500 while underpressure (e.g., compressed between the two flat surfaces 501 and 502) tobond with the first tensile layer 401 of the tensile element 400. FIG. 7shows the heating press 500 remaining in the open position and thesecond polymer sheet 302 now positioned on the first flat surface 501 ofthe tool 500, thereby permitting the heated second flat surface 502 ofthe tool 500 to contact the first polymer sheet 302 when the tool 500moves to the closed position by selectively moving the actuation handle520 to translate the upper platen 518 toward the lower platen 516.

FIG. 8 shows the tool 500 in the closed position after moving the secondsubstantially flat surface 502 of the upper platen 518 into contact withthe second polymer sheet 302. While the polymer sheets 301 and 302 andthe tensile element 400 are compressed between the first flat surface501 and the second flat surface 502 of the tool 500, the heatingelements 530 continue to apply heat 532 for heating the second flatsurface 502 to heat the first polymer sheet 301 in contact therewith.Accordingly, the heat 532 applied by the second substantially flatsurface 502 while in contact with the first polymer sheet 301 allows thefirst polymer sheet 301 to bond to the first tensile layer 401 of thetensile element 400. FIG. 9 shows the tool 500 in the open positionafter moving the second substantially flat surface 502 of the upperplaten 518 away from the first polymer sheet 301. Here, the peripheralbond 350 extends around the periphery of the chamber 300 to connect thefirst polymer sheet 301 (e.g., lower barrier portion 301) to the secondpolymer sheet 302 (e.g., upper barrier portion). Thereafter, pressurizedfluid (e.g., air) may be supplied into an area between the first polymersheet 301 and the second polymer sheet 302 to inflate the chamber 300via an inflation port (not shown) inserted between the sheets 301, 302at a port location along the peripheral bond 350. Once inflated, theinflation port may be closed by applying heat and pressure to the sheets301, 302 at the port location to once again seal the bond 350. Here, theperipheral bond 350 forms the sidewall 303 extending around theperiphery of the chamber 300, while the tensile element 400 is operativeto prevent the chamber 300 from expanding outward or otherwisedistending due to the pressure of the fluid within the internal cavityof the chamber 300. Namely, the tensile element 400 may limit expansionof the chamber 300 when under pressure to retain an intended shape ofsurfaces of the barrier portions 301 and 302.

In other configurations, the lower platen 516 also includes heatingelements for heating the first flat surface 501 while the second flatsurface 502 is simultaneously heated by the illustrated heating elements530. In these configurations, the heating of both the first and secondflat surfaces 501 and 502 allows the first polymer sheet 301 to bondwith the first tensile layer 401 and the second polymer sheet 302 tobond with the second tensile layer 402 concurrently without requiringthe second flat surface 502 to heat both of the polymer sheets 301 and302. As such, providing the lower platen 516 with heating elements 530eliminates the need to rotate/flip the polymer sheets 301 and 302 sothat the first polymer sheet 301 can be heated by the second flatsurface 502 after the second polymer sheet 302 is heated by the secondflat surface 502.

FIGS. 10 and 11 provide an article of footwear 10 a that includes anupper 100 and a sole structure 200 a attached to the upper 100. In viewof the substantial similarity in structure and function of thecomponents associated with the article of footwear 10 with respect tothe article of footwear 10 a, like reference numerals are usedhereinafter and in the drawings to identify like components while likereference numerals containing letter extensions are used to identifythose components that have been modified.

The sole structure 200 a includes the outsole 210 and the strobel 220arranged in the layered configuration. The sidewall 230 may surround theperimeter of the outsole 210 and may separate the outsole 210 and thestrobel 220 to define the cavity 240 therebetween. The outsole 210includes an inner surface 214 disposed on an opposite side of theoutsole 210 than the ground-engaging surface 212. The strobel 220includes a bottom surface 222 disposed on an opposite side of thestrobel 220 than the footbed 224. The bottom surface 222 opposes theinner surface 214 and the sidewall 230 may separate the bottom surface222 and the inner surface 214 to define a depth of the cavity 240.

In some configurations, the cavity 240 receives a fluid-filled chamber300 a filled with pressurized fluid (e.g., as air, nitrogen, helium,sulfur, hexafluoride, or liquids/gels) to enhance the cushioningcharacteristics of the footwear 10 a in response to ground-reactionforces. The fluid-filled chamber 300 a is substantially identical to thefluid-filled chamber 300 of FIGS. 1 and 2 except that the interiorcavity of the fluid-filled chamber 300 a does not receive the tensileelement 400. Accordingly, the chamber 300 a may include a lower barrierportion 301 a that opposes the outsole 210 and an upper barrier portion302 a disposed on an opposite side of the chamber 300 a than the lowerbarrier portion 301 a and opposing the strobel 220. The lower barrierportion 301 a may correspond to a first polymer sheet and the upperbarrier portion 302 may correspond to a second polymer sheet that joinsto the first polymer sheet to define a peripheral bond 350 a (FIGS.16-19 ) of the chamber 300 a. Here, the peripheral bond 350 a defines apredetermined area 340 a (FIGS. 14-19 ) associated with the interiorcavity that receives and retains the pressurized fluid therein.Accordingly, the peripheral bond 350 a forms the sidewall 303 thatextends around the periphery of the chamber 300 a to connect the lowerbarrier portion 301 a to the upper barrier portion 302 a.

FIG. 11 provides an exploded view of the article of footwear 10 ashowing the fluid-filled chamber 300 a retaining the pressurized fluid(e.g., air), the inner surface 214 of the outsole 210, and the bottomsurface 222 of the strobel 220. The length of the chamber 300 a mayextend between the first end 311, disposed proximate to the heel portion16 of the sole structure 200 a, and the second end 312, disposedproximate to the forefoot portion 12 of the sole structure 200 a. Thechamber 300 a may also include a thickness extending substantiallyperpendicular to the longitudinal axis L of the sole structure 200 a anda width extending between the lateral side 18 and the medial side 20.Accordingly, the length, the width, and the thickness of the chamber 300a may substantially occupy the cavity 240 defined by the inner surface214 and the bottom surface 222 and may extend through the forefoot,mid-foot, and heel portions 12, 14, 16, respectively, of the outsole210.

As with the fluid-filled chamber 300 of FIGS. 1 and 2 , the fluid-filledchamber 300 a may be manufactured using a heat press tool 500 a (FIGS.14-19 ) that applies heat and pressure to join the lower barrier portion301 a (e.g., first polymer sheet) and the upper barrier portion 302 a(e.g., second polymer sheet) together to define the peripheral bond 350a of the chamber 300 a. In some implementations, the jig 700 definingthe interior void 720 is employed to maintain a gap G between the firstpolymer sheet 301 a and the second polymer sheet 302 a within theinterior void 720. Here, the gap G has the predetermined area 340 a thatincludes a shape defined by the interior void 720 of the jig 700 suchthat the two polymer sheets 301 a and 302 a join together at locationsoutside the predetermined area 340 a to define the peripheral bond 350 aof the chamber 300 a.

FIGS. 12 and 13 provide the jig 700 for use with the heat press tool 500a (FIGS. 14-19 ) in maintaining the gap G between the first polymersheet 301 a and the second polymer sheet 302 a at the predetermined area340 a when forming the chamber 300 a. The interior void 720 defined bythe jig 700 is associated with an asymmetrical shape to form theasymmetrical chamber 300 a for incorporation into the article offootwear 10 a of FIGS. 10 and 11 . The jig 700 is substantially solidand is formed from one or more materials that impart properties ofstructural rigidity and high compressive strength when under load. Insome examples, the jig 700 is formed from silicon. In other examples,the jig 700 may be formed from any rigid materials that can withstandhigh temperatures such as, without limitation, leather, wood, silicon,and plastic. The jig 700 includes a substantially first flat surface 701and a substantially second flat surface 702 disposed on an opposite sideof the jig 700 than the first surface 701. The jig 700 defines a lengthextending from a first end 711 to a second end 712 in a directionparallel to the first and second surfaces 701 and 702, and a thicknessextending between the first and second surfaces 701 and 702. In someimplementations, the interior void 720 defined by the jig 700 is formedentirely through the first and second surfaces 701 and 702 of the jig700.

FIG. 13 provides a top view of the jig 700 showing the interior void 720defining a shape associated with the predetermined area 340 a of the gapG to be maintained between the first polymer sheet 301 a and the secondpolymer sheet 302 a. Accordingly, the interior void 720 may define alength slightly less than the lengths of the polymer sheets 301 a and302 a such that the gap is maintained within the interior void 720 andthe peripheral bond between the polymer sheets 301 a and 302 a is formedoutside of the interior void 720.

Referring to FIGS. 14-19 , a heat press tool 500 is provided andincludes a lower platen 516 and an upper platen 518 operable betweenopen and closed positions for joining the first polymer sheet 301 a andthe second polymer sheet 302 a together to define the peripheral bond350 a of the fluid-filled chamber 300 a for incorporation into thearticle of footwear 10 a of FIGS. 10 and 11 . The lower platen 516includes a substantially first flat surface 501 and the upper platen 518includes a substantially second flat surface 502. In someimplementations, the heating elements 530 are disposed in the upperplaten 518 for increasing the temperature (e.g., heating) the secondflat surface 502. The lower platen 516 may additionally or alternativelyinclude heating elements for increasing the temperature of the firstflat surface 501 without departing from the scope of the presentdisclosure. In some examples, the lower platen 516 is fixed and theupper platen 518 translates toward the lower platen 516 to close theheat press tool 500 and thereby apply pressure and heat 532 to the firstand second polymer sheets 301 a and 302 a disposed therebetween. Inother examples, the lower platen 516 and the upper platen 518 may eachtranslate toward one another or only the lower platen 516 may translatetoward the upper platen 518. In some examples, the lower platen 516includes heating elements to apply heat 532 in addition to, or in lieuof, applying heat 532 from heating elements 530 disposed in the upperplaten 518.

FIG. 14 shows the heat press tool 500 in the open position and the jig700 positioned in a first position on the substantially first flatsurface 501 of the tool 500, the first polymer sheet 301 a positioned onthe jig 700, and the second polymer sheet 302 a positioned on the firstpolymer sheet 301 a. The first position of the jig 700 corresponds tothe first flat surface 701 in opposed contact with the first flatsurface 501 of the tool 500 and the second flat surface 702 in opposedcontact with the first polymer sheet 301 a. FIG. 14 shows gravitycausing the polymer sheets 301 a and 302 a to sag relative to the firstflat surface 701 at locations within the interior void 720. As willbecome apparent, the interior void 720 is operative to maintain the gapG between the first polymer sheet 301 a and the second polymer sheet 302a within the interior void 720 such that the first polymer sheet 301 aand the second polymer sheet 302 a are prevented from joining, orotherwise bonding, to one another at the predetermined area 340 aincluding a shape defined by the interior void 720 of the jig 700. Inshort, the gap G prevents the sheets 301 a, 302 a from contacting oneanother and, as such, prevents the sheets 301 a, 302 a from bonding toone another when heat and pressure are applied by the tool 500. In someexamples, the heating elements 530 begin to heat the second flat surface502 to a predetermined temperature while the tool 500 is open. As such,the second flat surface 502 may be at a predetermined temperature priorto engaging the second polymer sheet 302 a.

The tool 500 may close by translating the upper platen 518 toward thelower platen 516. FIG. 15 shows the tool 500 closed by moving the secondsubstantially flat surface 502 of the upper platen 518 into contact withthe second polymer sheet 302 a. Moving the second flat surface 502 intocontact with the second polymer sheet 302 a causes the jig 700, thefirst polymer sheet 301 a, and the second polymer sheet 302 a tocompress between the first flat surface 501 and the second flat surface502 of the heat press tool 500. More specifically, the first polymersheet 301 a and the second polymer sheet 302 a compress against oneanother between the second flat surface 502 of the tool 500 and the jig700 (e.g., at locations outside the interior void 720), while the gap Gis maintained between the two polymer sheets 301 a and 302 a within theinterior void 720 when the tool 500 is in the closed position. Thus, theinterior void 720 defines a shape including the predetermined area 340 asuch that the gap G is maintained between the two polymer sheets 301 aand 302 a due to gravity causing the polymer sheets 301 a and 302 a tosag within the interior void 720. Concurrently, the heating elements 530associated with the upper platen 518 heat the second flat surface 502 ofthe tool 500 to the predetermined temperature to heat the second polymersheet 302 a in contact therewith. In some examples, heating the secondflat surface 502 of the tool 500 includes heating an entire surfacesecond flat surface 502. The predetermined temperature includes atemperature suitable for allowing the second polymer sheet 302 a to joinwith the first polymer sheet 301 a at locations outside of the interiorvoid 720 defined by the jig 700 to define the peripheral bond 350 a ofthe chamber 300 a. In other examples, the lower platen 516 additionallyor alternatively includes heating elements 530 for heating the firstflat surface 501 to heat the first polymer sheet 301 a, as describedabove with respect to the fluid-filled chamber 300.

FIG. 16 shows the heat press tool 500 in the open position by moving thesecond substantially flat surface 502 of the upper platen 518 away fromthe second polymer sheet 302 a after joining the first polymer sheet 301a and the second polymer sheet 302 a to define the peripheral bond 350 aat the locations outside of the interior void 720. The peripheral bond350 a may be further strengthened by heating the first polymer sheet 301a and applying pressure to compress the first polymer sheet 301 aagainst the second polymer sheet 302 a at the locations outside of theinterior void 720. Accordingly, in some optional configurations, the twopolymer sheets 301 a and 302 a may be rotated 180° (e.g., flipped) sothat the first polymer sheet 301 a can be heated by the substantiallysecond flat surface 502 a in configurations when the first platen 516does not include heating elements 530. Moreover, the chamber 300 adefines an asymmetrical shape corresponding to the outline of a foot.Thus, in order to maintain the gap G between the first polymer sheet 301a and the second polymer sheet 302 a at the locations within theinterior void 720, the jig 700 must also be rotated 180° (e.g., flipped)so that the second flat surface 702 of the jig 700 is positioned incontact with the substantially first flat surface 501 of the tool 500and the second polymer sheet 302 a is positioned in contact with thefirst flat surface 701 of the jig 700. FIG. 17 shows the heat press tool500 remaining in the open position while the jig 700 is positioned in asecond position on the first flat surface 501 of the tool 500 afterrotating the jig 700 180°. In this view, the second polymer sheet 302 ais positioned on the jig 700. Here, the second position of the jig 700corresponds to the second flat surface 702 of the jig 700 now positionedon the first flat surface 501 of the tool 500 to allow the secondpolymer sheet 302 a to be positioned in contact with the jig 700. In theexample, positioning the second polymer sheet 302 a in contact with thejig 700 includes positioning the peripheral bond 350 a on the jig 700.

FIG. 18 shows the tool 500 in the closed position after moving thesecond substantially flat surface 502 of the upper platen 518 intocontact with the first polymer sheet 302 a. The gap G between the firstpolymer sheet 301 a and the second polymer sheet 302 a is maintained atthe locations within the interior void 720 defined by the jig 700. Whilethe polymer sheets 301 a and 302 a are compressed between the jig 700and the second flat surface 502 of the tool 500, the second flat surface502 heated by the heating elements 530 now heats (via heat 532) thefirst polymer sheet 301 a in contact therewith to further strengthen theperipheral bond 350 a at the locations outside of the interior void 720defined by the jig 700. In some configurations, a bond inhibitor isapplied between the polymer sheets 301 a and 302 a within thepredetermined area 340 a to prevent the polymer sheets 301 a and 302 afrom bonding to each other to create the gap G. The bond inhibitor mayinclude placing a printed pigment-based ink within the predeterminedarea 340 a associated with the gap G. For instance, the pigment-basedink may be printed on a sheet of fabric or paper and the sheet may beplaced within the predetermined area 340 a. In some configurations, thebond inhibitor may include spraying or pressing a pigmented-based inkwithin the predetermined area 340 a.

In some configurations, the interior cavity of the fluid-filled chamber300 a also receives the tensile element 400 of the article of footwear10 of FIGS. 1-9 . Here, the lower tensile layer 401 may attach to thelower barrier portion 301 a, the upper tensile layer 402 may attach tothe upper barrier portion 302 a, and the plurality of tensile elements430 may extend between the lower and upper tensile layers 401 and 402,respectively, of the tensile element 400. As with the chamber 300 ofFIGS. 1-9 , thermobonding may be used to secure the tensile element 400to the chamber 300 a, and thereby prevent the chamber 300 a fromexpanding outward or otherwise distending due to the pressure of thefluid within the internal cavity of the chamber 300 a. Namely, thetensile element 400 may limit expansion of the chamber 300 a when underpressure to retain an intended shape of surfaces of the barrier portions301 a and 302 a.

FIG. 19 shows the heat press tool 500 in the open position after movingthe second substantially flat surface 502 of the upper platen 518 awayfrom the first polymer sheet 301 a. Here, the peripheral bond 350 aextends around the periphery of the chamber 300 a to connect the firstpolymer sheet 301 a (e.g., lower barrier portion) to the second polymersheet 302 a (e.g., upper barrier portion). Thereafter, the pressurizedfluid (e.g., air) may be supplied into an area between the first polymersheet 301 a and the second polymer sheet 302 a to inflate the chamber300 a in a similar fashion as described above with respect to thefluid-filled chamber 300. Here, the peripheral bond 350 a forms thesidewall 303 extending around the periphery of the chamber 300 a. Inview of the forgoing, the steps outlined in FIGS. 14-16 where heat 532is applied directly to the second polymer sheet 302 a is sufficient tojoin the two polymer sheets 301 a and 302 a together to define theperipheral bond 350 a when the two polymer sheets 301 a and 302 a arecompressed together. Thus, the pressurized fluid (e.g., air) may besupplied after joining the first polymer sheet 301 a and the secondpolymer sheet 302 a as outlined in FIGS. 14-16 . However, the stepsoutlined in FIGS. 16-18 , that require rotating (e.g., flipping) of bothpolymer sheets 301 a and 302 a and the jig 700 180° are optional stepsthat may serve to further strengthen the peripheral bond 350 atherebetween.

FIGS. 20 and 21 provide a jig 700 b for use with a heat press tool 500(FIGS. 22-26 ) to form a fluid-filled chamber 300 b (FIG. 27 ) having asymmetrical shape. More specifically, the jig 700 b defines an interiorvoid 720 b including a symmetrical shape for forming the chamber 300 bto provide cushioning for a heel of a foot. The chamber 300 b may beincorporated into the heel portion 16 of either of the articles offootwear 10, 10 a in addition to, or in lieu of, the chambers 300, 300a. Thus, the chamber 300 b defines a length that is shorter than alength of the sole structure 200, 200 a. Other chambers may be similarlymanufactured to reside in the forefoot portion 12, the mid-foot portion14, or a combination of the heel and mid-foot portions 16, 14,respectively, or the forefoot and mid-foot portions 12, 14,respectively. As with the chambers 300, 300 a of FIGS. 1-19 , thechamber 300 b includes a lower barrier portion 301 b (e.g., firstpolymer sheet), an upper barrier portion 302 b, and a peripheral bond350 b (FIGS. 24-26 ) joining the first and second polymer sheets 301 band 302 b to define a sidewall 303 b extending around the periphery ofthe fluid-filled chamber 300 b. As with the jig 700 of FIGS. 12 and 13 ,the jig 700 b is substantially solid and formed from the one or morematerials that impart properties of structure rigidity and highcompressive strength when under load, e.g., the jig 700 b may be formedfrom silicon or wood. The jig 700 b includes a substantially first flatsurface 701 b and a substantially second flat surface 702 b disposed onan opposite side of the jig 700 b than the first surface 701 b. The jig700 b defines a length extending from a first end 711 b to a second end712 b in a direction substantially parallel to the first and secondsurfaces 701 b and 702 b, and a thickness extending between the firstand second surfaces 701 b and 702 b. In some implementations, theinterior void 720 b defined by the jig 700 b is formed entirely throughthe first and second surfaces 701 b and 702 b of the jig 700 b.

FIG. 21 provides a top view of the jig 700 b showing the interior void720 b defining a shape that is symmetrical about a longitudinal axis Lof the jig 700 b and associated with a predetermined area 340 b (FIG. 22) of a gap G (FIG. 22 ) to be maintained between the first polymer sheet301 b and the second polymer sheet 302 b. Accordingly, the interior void720 b may define a length slightly less than the lengths of the polymersheets 301 b and 302 b such that the gap G is maintained within theinterior void 720 and the peripheral bond 350 b between the polymersheets 301 b and 302 b is formed at locations outside of the interiorvoid 720 b.

Referring to FIGS. 22-26 , the heat press tool 500 is provided andincludes a lower platen 516 and an upper platen 518 operable betweenopen and closed positions for joining the first polymer sheet 301 b andthe second polymer sheet 302 b together to define the peripheral bond350 b of the fluid-filled chamber 300 b (FIG. 27 ) for incorporationinto the heel region 16 of an article of footwear 10, 10 a. As with theheat press tools 500 of FIGS. 3-19 , the lower platen 516 of the heatpress tool 500 includes a substantially first flat surface 501 and theupper platen 518 of the heat press tool 500 includes a substantiallysecond flat surface 502. In some implementations, the heating elements530 are disposed in the upper platen 518 for increasing the temperature(e.g., heating) of the second flat surface 502. The lower platen 516 mayadditionally or alternatively include heating elements for increasingthe temperature of the first flat surface 501 without departing from thescope of the present disclosure. In some examples, the lower platen 516is fixed and the upper platen 518 translates toward the lower platen 516to close the heat press tool 500 and thereby apply pressure and heat tothe first and second polymer sheets 301 b and 302 b disposedtherebetween. In other examples, the lower platen 516 and the upperplaten 518 may each translate toward one another or only the lowerpatent 516 may translate toward the upper platen 518.

FIG. 22 shows the heat press tool 500 in the open position and the jig700 b positioned in the first position on the first flat surface 501 ofthe tool 500, the first polymer sheet 301 b positioned on the jig 700 b,and the second polymer sheet 302 b positioned on the first polymer sheet301 b. The first position of the jig 700 b corresponds to the first flatsurface 701 b in opposed contact with the first flat surface 501 of thetool 500 and the second flat surface 702 b in opposed contact with thefirst polymer sheet 301 b. FIG. 22 shows gravity causing the polymersheets 301 b and 302 b to sag relative to the first flat surface 701 bat locations within the interior void 720 b. As with the interior void720 defined by the jig 700 of FIGS. 12-19 , the interior void 720 b isoperative to maintain the gap G between the first polymer sheet 301 band the second polymer sheet 302 b within the interior void 720 b suchthat the first polymer sheet 301 b and the second polymer sheet 302 bare prevented from joining, or otherwise bonding, to one another at apredetermined area 340 b including a shape defined by the interior void720 b of the jig 700 b. In some examples, the heating elements 530 beginto heat the second flat surface 502 to a predetermined temperature whilethe tool 500 is open. As such, the second flat surface 502 may be at apredetermined temperature prior to engaging the second polymer sheet 302b.

The tool 500 may closed by translating the upper platen 518 toward thelower platen 516. FIG. 23 shows the tool 500 being closed by moving thesecond substantially flat surface 502 of the upper platen 518 intocontact with the second polymer sheet 302 b. Moving the second flatsurface 502 into contact with the second polymer sheet 302 b causes thejig 700 b, the first polymer sheet 301 b, and the second polymer sheet302 b to compress between the first flat surface 501 and the second flatsurface 502 of the heating tool 500. More specifically, the firstpolymer sheet 301 b and the second polymer sheet 302 b compress againstone another between the second flat surface 502 of the tool 500 and thejig 700 b (e.g., at locations outside the interior void 720 b), whilethe gap G is maintained between the two polymer sheets 301 a and 302 bat the predetermined area 340 b within the interior void 720 b when thetool 500 is in the closed position. Thus, the interior void 720 bdefines a shape including the predetermined area 340 b such that the gapG is maintained between the two polymer sheets 301 b and 302 b do togravity causing the polymer sheets 301 b and 302 b to sag within theinterior void 720 b. Concurrently, the heating elements 530 associatedwith the upper platen 518 apply heat 532 to the second flat surface 502of the tool 500 to a predetermined temperature to heat the secondpolymer sheet 302 b in contact therewith. In some examples, heating thesecond flat surface 502 of the tool 500 includes heating the entiresecond flat surface 502. The predetermined temperature includes atemperature suitable for allowing the second polymer sheet 302 b to joinwith the first polymer sheet 301 b at locations outside of the interiorvoid 720 b defined by the jig 700 b to define the peripheral bond 350 bof the chamber 300 b. In other examples, the lower platen 516 includesheating elements 530 for heating the first flat surface 501 to heat thefirst polymer sheet 301 b simultaneously with the second polymer sheet302 b.

FIG. 24 shows the heating press tool 500 in the open position by movingthe second substantially flat surface 502 of the upper platen 518 awayfrom the second polymer sheet 302 b after joining the first polymersheet 301 b and the second polymer sheet 302 b to define the peripheralbond 350 b at the locations outside of the interior void 720 b definedby the jig 700 b. The peripheral bond 350 b may be further strengthenedby heating the first polymer sheet 301 b and applying pressure tocompress the first polymer sheet 301 b against the second polymer sheet302 b at the locations outside of the interior void 720 b. Accordingly,the two polymer sheets 301 b and 302 b may be rotated 180° (e.g.,flipped) so that the first polymer sheet 301 b can be heated by thesubstantially second flat surface 502 in configurations when the firstplaten 516 does not include heating elements. As the shape defined bythe interior void 720 b of the jig 700 b is symmetrical, the jig 700 bmay remain in the first position on the first flat surface 501 of thetool 500 while the second polymer sheet 302 b is positioned in contactwith the first flat surface 701 b of the jig 700 b. FIG. 25 shows theheating press tool 500 remaining in the open position while the jig 700b remains positioned in the first position on the first flat surface 501of the tool 500 after the second polymer sheet 302 b is positioned onthe jig 700 b underneath the first polymer sheet 301 b. In the example,positioning the second polymer sheet 302 b in contact with the jig 700 bincludes positioning the peripheral bond 350 b on the jig 700 b.

FIG. 26 shows the tool 500 in the closed position after moving thesecond substantially flat surface 502 of the upper platen 518 intocontact with the first polymer sheet 301 b. The gap G between the firstpolymer sheet 301 b and the second polymer sheet 302 b is maintained atthe locations within the interior void 720 b defined by the jig 700 b.While the polymer sheets 301 b and 302 b are compressed between the jig700 b and the second flat surface 502 of the tool 500, the second flatsurface 502 heated by the heating elements 530 now applies the heat 532to the first polymer sheet 301 b in contact therewith to furtherstrengthen the peripheral bond 350 b at the locations outside of theinterior void 720 b defined by the jig 700 b.

FIG. 27 provides a perspective view of the heating press tool 500 in theopen position after forming the chamber 300 b by joining the firstpolymer sheet 301 b to the second polymer sheet 301 b at the peripheralbond 350 b. Here, the peripheral bond 350 b extends around the peripheryof the chamber 300 b to connect the first polymer sheet 301 b (e.g.,lower barrier portion) to the second polymer sheet 302 b (e.g., upperbarrier portion). Thereafter, pressurized fluid (e.g., air) may besupplied into an area between the first polymer sheet 301 b and thesecond polymer sheet 302 b to inflate the chamber 300 b, in the mannerdescribed above with respect to the fluid-filled chamber 300. Here, theperipheral bond 350 b forms the sidewall 303 b extending around theperiphery of the chamber 300 b. Accordingly, the fluid-filled chamber300 b may be incorporated into any of the articles of footwear 10, 10 ato provide cushioning for the foot in the heel portion 16.

Referring to FIGS. 28-33 , in some implementations, a first thermoformedpolymer sheet 301 c and a second thermoformed polymer sheet 302 c jointogether at a peripheral bond 350 d to form a fluid-filled chamber 300 c(FIG. 32 ). For instance, the chamber 300 c may be incorporated into theheel portion 16 of either of the articles of footwear 10, 10 a inaddition to, or in lieu of, the chambers 300, 300 a. The heat press tool500 is provided and includes a lower platen 516 and an upper platen 518operable between open and closed positions. The lower platen 516 andupper platen 518 may be used to join the first thermoformed polymersheet 301 c and the second thermoformed polymer sheet 302 c together bydefining a peripheral bond 350 c of the fluid-filled chamber 300 c (FIG.33 ). Once formed, the fluid-filled chamber 300 c may be incorporatedinto an article of footwear 10, 10 a. The sheets 301 c and 302 c may bethermoformed to define a shape of the fluid-filled chamber 300 c. Aswith the heat press tools 500 of FIGS. 3-19 and 22-26 , the lower platen516 of the heat press tool 500 includes a substantially first flatsurface 501 and the upper platen 518 of the heat press tool 500 includesa substantially second flat surface 502. In some implementations, theheating elements 530 are disposed in the upper platen 518 for increasingthe temperature (e.g., heating) of the second flat surface 502. Thelower platen 516 may additionally or alternatively include heatingelements for increasing the temperature of the first flat surface 501without departing from the scope of the present disclosure. In someexamples, the lower platen 516 is fixed and the upper platen 518translates toward the lower platen 516 to close the heat press tool 500and thereby apply pressure and heat to the first and second thermoformedpolymer sheets 301 c and 302 c disposed therebetween. In other examples,the lower platen 516 and the upper platen 518 may each translate towardone another or only the lower platen 516 may translate toward the upperplaten 518.

FIG. 28 shows the heat press tool 500 in the open position and a jig 700c positioned on the first flat surface 501 of the tool 500, the firstthermoformed polymer sheet 301 c positioned on the jig 700 c, and thesecond thermoformed polymer sheet 302 c positioned on the first polymersheet 301 c. The jig 700 c includes a first flat surface 701 c inopposed contact with the first flat surface 501 of the tool 500 and asecond flat surface 702 c in opposed contact with the first thermoformedpolymer sheet 301 c. The jig 700 c defines an interior void 720 c thatmay accommodate the surface profile of the first thermoformed polymersheet 301 c and the surface profile of the second thermoformed polymersheet 302 c may nest with the first thermoformed polymer sheet 301 cwithin the interior void 720 c. In some examples, the polymer sheet 302c is not thermoformed and is simply positioned on top of the firstthermoformed polymer sheet 301 c, whereby gravity causes the secondpolymer sheet 302 c to sag relative to the first flat surface 701 c atlocations within the interior void 720 c. In some examples, the polymersheets 301 c and 302 c are thermoformed to include shapes that arecurved or more arcuate. The interior void 720 c compensates for athickness or depth of the chamber 300 c within a predetermined area 340c where the thermoformed polymer sheets 301 c and 302 c are preventedfrom joining, or otherwise, bonding to one another. In some examples,the heating elements 530 begin to heat the second flat surface 502 to apredetermined temperature while the tool 500 is open. As such, thesecond flat surface 502 may be at a predetermined temperature prior toengaging the second thermoformed polymer sheet 302 c. The jig 700 c maydefine the interior void 720 c having a symmetrical shape to form thefluid-filled chamber 300 c (FIG. 33 ) having a corresponding symmetricalshape to provide cushioning for a heel of a foot. In other examples, thejig 700 c, the heat press tool 500, and the use of at least onethermoformed polymer sheets 301 c and 302 c may form a fluid-filledchamber having a shape (e.g., asymmetrical) substantially identical tothe fluid-filled chambers 300, 300 a.

The tool 500 may be closed by translating the upper platen 518 towardthe lower platen 516. FIG. 29 shows the tool 500 being closed by movingthe second substantially flat surface 502 of the upper platen 518 intocontact with the second thermoformed polymer sheet 302 c. Moving thesecond flat surface 502 into contact with the second thermoformedpolymer sheet 302 c causes the jig 700 c, the first thermoformed polymersheet 301 c, and the second thermoformed polymer sheet 302 c to compressbetween the first flat surface 501 and the second flat surface 502 ofthe heating tool 500. More specifically, the first thermoformed polymersheet 301 c and the second thermoformed polymer sheet 302 c compressagainst one another between the second flat surface 502 of the tool 500and the jig 700 c (e.g., at locations outside the interior void 720 c),while the portions of the two polymer sheets 301 c and 302 c withinpredetermined area 340 c that are not to be joined/bonded nest withinthe interior void 720 c when the tool 500 is in the closed position.Concurrently, the heating elements 530 associated with the upper platen518 apply heat 532 to the second flat surface 502 of the tool 500 to apredetermined temperature to heat the second thermoformed polymer sheet302 c in contact therewith. In some examples, heating the second flatsurface 502 of the tool 500 includes heating the entire second flatsurface 502. The predetermined temperature includes a temperaturesuitable for allowing the second thermoformed polymer sheet 302 c tojoin with the first thermoformed polymer sheet 301 c at locationsoutside of the interior void 720 c defined by the jig 700 c to definethe peripheral bond 350 c of the chamber 300 c.

FIG. 30 shows the heating press tool 500 in the open position by movingthe second substantially flat surface 502 of the upper platen 518 awayfrom the second thermoformed polymer sheet 302 c after joining the firstthermoformed polymer sheet 301 c and the second thermoformed polymersheet 302 c to define the peripheral bond 350 c at the locations outsideof the interior void 720 c defined by the jig 700 c. Conversely to theperipheral bonds 350, 350 a, 350 b of FIGS. 1-27 , the peripheral bond350 c may form an offset seam located around the peripheral edges of thesheets 301 c and 302 c.

FIG. 31 shows the first and second thermoformed polymer sheets 301 c and302 c removed from the tool 500 after forming the peripheral bond 350 cat the locations outside the predetermined area 340 c. Here, the chamber300 c is deflated. In some examples, one of the thermoformed polymersheets 301 c and 302 c defines a port 304 operative to fluidly couplethe chamber 300 c to a fluid source 800 containing a pressurized fluid(e.g., air) 850. In the example shown, the port 304 receives a conduit802 extending from the fluid source 800 to supply the pressurized fluid850 into the port 304 to inflate the chamber 300 c.

FIG. 32 shows the fluid source 800 inflating the chamber 300 c bydelivering the pressurized fluid 850 through the port 304 via theconduit 802 and into an internal cavity between the first and secondthermoformed polymer sheets 301 c and 302 c. The peripheral bond 350 cseals the chamber 300 c and allows pressure P within the internal cavity352 to increase. Here, the pressure P causes inversion of the secondthermoformed polymer sheet 302 c such that the thermoformed polymersheets 301 c and 302 c expand away from one another as the chamber 300 cinflates. Here, the peripheral bond 350 c forms the sidewall 303 cextending around the periphery of the chamber 300 c. FIG. 33 provides aperspective view of the chamber 300 c formed after inflating the chamber300 c and sealing the port 304. Here, the chamber 300 c may beincorporated into the heel portion 16 of any of the articles of thefootwear 10, 10 a. The peripheral bond 350 c associated with the offsetseam forms the sidewall 303 c extending around the periphery of thechamber 300 c. In other configurations, the jig 700 c, the heat presstool 500, and the use of at least one thermoformed polymer sheets 301 cand 302 c may form a fluid-filled chamber having any shape suitable toprovide cushioning for the foot in at least one of the forefoot,mid-foot, and heel portions 12, 14, 16, respectively, of either of thearticles of footwear 10, 10 a.

The following Clauses provide configurations for forming a chamberdescribed above.

Clause 1: A method of forming a chamber, the method comprisingpositioning a first polymer sheet on a substantially first flat surfaceof a tool, positioning a second polymer sheet on the first polymersheet, moving a second substantially flat surface of the tool intocontact with the second polymer sheet, maintaining a gap between thefirst polymer sheet and the second polymer sheet at a predeterminedarea, heating one of the two substantially flat surfaces of the tool toheat one of the first polymer sheet and the second polymer sheet andjoining the first polymer sheet and the second polymer sheet together atlocations outside of the predetermined area to define a peripheral bondof the chamber.

Clause 2: The method of Clause 1, wherein maintaining the gap betweenthe first polymer sheet and the second polymer sheet includes adding atensile element defining the predetermined area between the firstpolymer sheet and the second polymer sheet.

Clause 3: The method of Clause 2, wherein heating the one of the twosubstantially flat surfaces of the tool heats an entire surface of theone of the two polymer sheets.

Clause 4: The method of Clause 2, wherein adding the tensile elementdefining the predetermined area between the first polymer sheet and thesecond polymer sheet includes positioning a first tensile layer of thetensile element in contact with the first polymer sheet and positioninga second tensile layer of the tensile element in contact with the secondpolymer sheet.

Clause 5: The method of Clause 4, wherein heating one of the twosubstantially flat surfaces of the tool bonds one of the first polymersheet and the second polymer sheet to a respective one of the firsttensile layer and the second tensile layer.

Clause 6: The method of Clause 5, further comprising moving the secondsubstantially flat surface of the tool away from the second polymersheet after joining the first polymer sheet and the second polymersheet, positioning the second polymer sheet on the substantially firstflat surface of the tool, moving the second substantially flat surfaceof the tool into contact with the first polymer sheet, and heating theone of the two substantially flat surfaces of the tool to heat the otherof the first polymer sheet and the second polymer sheet.

Clause 7: The method of Clause 6, wherein heating the other of the firstpolymer sheet and the second polymer sheet causes the other of the firstpolymer sheet and the second polymer sheet to bond to a respective oneof the first tensile layer and the second tensile layer.

Clause 8: The method of Clause 4, further comprising heating the otherof the two substantially flat surfaces of the tool to heat a surface ofthe other of the first polymer sheet and the second polymer sheet.

Clause 9: The method of Clause 8, wherein joining the first polymersheet and the second polymer sheet together at locations outside of thepredetermined area includes joining the first polymer sheet to the firsttensile layer and joining the second polymer sheet to the second tensilelayer at locations within the predetermined area.

Clause 10: The method of Clause 1, further comprising positioning a jigbetween the first polymer sheet and the substantially first flat surfaceof the tool.

Clause 11: The method of Clause 10, wherein maintaining the gap betweenthe first polymer sheet and the second polymer sheet at thepredetermined area includes maintaining the gap between the firstpolymer sheet and the second polymer sheet within a void defined by thejig.

Clause 12: The method of Clause 1, further comprising supplying apressurized fluid into an area between the first polymer sheet and thesecond polymer sheet after joining the first polymer sheet and thesecond polymer sheet together to inflate the chamber.

Clause 13: A method of forming a chamber, the method comprisingpositioning a jig defining an interior void in a first position on afirst surface of a tool, positioning a first polymer sheet on the jig,positioning a second polymer sheet on the first polymer sheet, moving asecond surface of the tool into contact with the second polymer sheet,heating the tool to heat one of the first polymer sheet and the secondpolymer sheet, and joining the first polymer sheet and the secondpolymer sheet together at locations outside of the interior void definedby the jig to define a peripheral bond of the chamber.

Clause 14: The method of Clause 13, further comprising maintaining a gapbetween the first polymer sheet and the second polymer sheet, the gaphaving a predetermined area including a shape defined by the interiorvoid of the jig.

Clause 15: The method of Clause 14, wherein heating the tool to heat theone of the first polymer sheet and the second polymer sheet includesheating the second surface of the tool to heat the second polymer sheet.

Clause 16: The method of Clause 15, further comprising moving the secondsurface of the tool away from the second polymer sheet after heating thesecond polymer sheet, positioning the second polymer sheet on the jig,moving the second surface of the tool into contact with the firstpolymer sheet, and heating the second surface of the tool to heat thefirst polymer sheet.

Clause 17: The method of Clause 16, wherein positioning the secondpolymer sheet on the jig includes positioning the peripheral bond on thejig.

Clause 18: The method of Clause 15, further comprising moving the secondsurface of the tool away from the second polymer sheet after heating thesecond polymer sheet, rotating the jig 180°, positioning the jig in asecond position on the first surface of the tool after rotating the jig180°, positioning the second polymer sheet on the jig, moving the secondsurface of the tool into contact with the first polymer sheet, heatingthe second surface of the tool to heat the first polymer sheet, andjoining the first polymer sheet and the second polymer sheet together atlocations outside of the interior void defined by the jig to define theperipheral bond of the chamber.

Clause 19: The method of Clause 18, further comprising maintaining thegap between the first polymer sheet and the second polymer sheet at thepredetermined area within the interior void defined by the jig.

Clause 20: The method of Clause 18, wherein positioning the secondpolymer sheet on the jig includes positioning the peripheral bond on thejig when the jig is in the second position.

Clause 21: The method of Clause 13, further comprising supplying apressurized fluid into an area between the first polymer sheet and thesecond polymer sheet after joining the first polymer sheet and thesecond polymer sheet together to inflate the chamber.

Clause 22: The method of Clause 13, wherein positioning a first polymersheet on the jig includes positioning a first thermoformed polymer sheeton the jig.

Clause 23: The method of Clause 22, wherein positioning a second polymersheet on the first polymer sheet comprises positioning a secondthermoformed polymer sheet on the first thermoformed polymer sheet.

The foregoing description has been provided for purposes of illustrationand description. It is not intended to be exhaustive or to limit thedisclosure. Individual elements or features of a particularconfiguration are generally not limited to that particularconfiguration, but, where applicable, are interchangeable and can beused in a selected configuration, even if not specifically shown ordescribed. The same may also be varied in many ways. Such variations arenot to be regarded as a departure from the disclosure, and all suchmodifications are intended to be included within the scope of thedisclosure.

What is claimed is:
 1. A method of forming a fluid-filled chamber, themethod comprising: positioning a jig defining an interior void in afirst position on a first surface of a tool; positioning a first polymersheet on the jig; positioning a second polymer sheet on the firstpolymer sheet; fixing a relative position of outer edges of the firstpolymer sheet and the second polymer sheet; allowing the first polymersheet to sag and move away from the second polymer sheet to create a gapbetween the first polymer sheet and the second polymer sheet at alocation of the interior void; moving a second surface of the tool intocontact with the second polymer sheet; heating the second surface of thetool to heat the second polymer sheet; and joining the first polymersheet and the second polymer sheet together at locations outside of theinterior void defined by the jig to define a peripheral bond of thechamber, the chamber having a same shape as a shape of the interiorvoid.
 2. The method of claim 1, wherein allowing the first polymer sheetto sag and move away from the second polymer sheet includes allowing thefirst polymer sheet to enter the interior void of the jig.
 3. The methodof claim 1, further comprising positioning the heated second polymersheet on the jig.
 4. The method of claim 3, further comprising movingthe second surface of the tool into contact with the first polymersheet.
 5. The method of claim 4, further comprising heating the secondsurface of the tool to heat the first polymer sheet.
 6. The method ofclaim 1, wherein fixing a relative position of outer edges of the firstpolymer sheet and the second polymer sheet includes clamping the outeredges between the second surface of the tool and the jig.
 7. The methodof claim 1, wherein heating the second surface of the tool heats anentire surface of the second polymer sheet.
 8. The method of claim 1,further comprising supplying a pressurized fluid into an area betweenthe first polymer sheet and the second polymer sheet after joining thefirst polymer sheet and the second polymer sheet together to inflate thechamber.
 9. The method of claim 1, further comprising incorporating thefluid-filled chamber into a sole structure.
 10. The method of claim 1,further comprising incorporating the fluid-filled chamber into anarticle of footwear.
 11. A method of forming a fluid-filled chamber, themethod comprising: positioning a jig defining an interior void in afirst position on a first surface of a tool; positioning a first polymersheet on the jig; positioning a second polymer sheet on the firstpolymer sheet; clamping the first polymer sheet and the second polymersheet between a second surface of the tool and the jig; allowing thefirst polymer sheet to sag and move away from the second polymer sheetto create a gap between the first polymer sheet and the second polymersheet at a location of the interior void; heating the second surface ofthe tool to heat the second polymer sheet; and joining the first polymersheet and the second polymer sheet together at locations outside of theinterior void defined by the jig to define a peripheral bond of thechamber, the chamber having a same shape as a shape of the interiorvoid.
 12. The method of claim 11, wherein allowing the first polymersheet to sag and move away from the second polymer sheet includesallowing the first polymer sheet to enter the interior void of the jig.13. The method of claim 11, further comprising positioning the heatedsecond polymer sheet on the jig.
 14. The method of claim 13, furthercomprising moving the second surface of the tool into contact with thefirst polymer sheet.
 15. The method of claim 14, further comprisingheating the second surface of the tool to heat the first polymer sheet.16. The method of claim 11, further comprising aligning outer edges ofthe first polymer sheet with outer edges of the second polymer sheetbefore clamping the first polymer sheet and the second polymer sheet.17. The method of claim 11, wherein heating the second surface of thetool heats an entire surface of the second polymer sheet.
 18. The methodof claim 11, further comprising supplying a pressurized fluid into anarea between the first polymer sheet and the second polymer sheet afterjoining the first polymer sheet and the second polymer sheet together toinflate the chamber.
 19. The method of claim 11, further comprisingincorporating the fluid-filled chamber into a sole structure.
 20. Themethod of claim 11, further comprising incorporating the fluid-filledchamber into an article of footwear.